host-mkpasswd: new package

Since the addition of root password setting support in buildroot, there have
been a few bug reports in this area ([1], [2]). In these cases, the system
mkpasswd did either not work, or did not provide the options we expect, like
-m <method>.

This patch adds a mkpasswd host package, based on the sources from whois. When
a non-empty root password is set, this package is used as a dependency.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>

[1] http://lists.busybox.net/pipermail/buildroot/2013-July/075771.html
[2] http://lists.busybox.net/pipermail/buildroot/2013-July/075869.html



[Thomas P: use $(INSTALL) instead of install, put -lcrypt at the end
of build command line to allow gcc to find the crypt() function in
lcrypt.]

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>